Stockholders' Equity and Noncontrolling Interests - Statutory Capital and Surplus and Net Income of Insurance Entities in Accordance with Statutory Accounting Practices (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Life
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	$ 1,989,586	$ 2,141,573
Statutory net income	59,909	46,820	$ 82,101
Property & Casualty
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	1,183,913	1,162,761
Statutory net income	$ 66,680	$ 72,267	$ 48,378